Not Applicable
This invention relates to a stent delivery and dilation catheter system, such as the kind used in percutaneous transluininal coronary angioplasty (PTCA) procedures. More particularly, it relates to a stent delivery catheter employing a rolling retractable sheath which may be retracted to release a self-expanding or balloon expandable stent and which may also be employed as a dilatation balloon for expanding a vessel prior to stent delivery.
In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the ostium of the desired coronary artery. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. A balloon catheter is advanced over the guide wire to the treatment site. The balloon is then expanded to reopen the artery. The catheter may have a guide wire lumen which is as long as the catheter (such as with an over the wire catheterxe2x80x94OTW) or it may be a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter. Alternatively, a fixed wire balloon catheter could be used. This device features a guide wire which is affixed to the catheter and cannot be removed.
To help prevent arterial closure, repair dissection, or prevent restenosis, a physician can implant an intravascular prosthesis, or a stent, for maintaining vascular patency inside the artery at the lesion. The stent may either be a self-expanding stent or a balloon expandable stent. For the latter type, the stent is often delivered on a balloon and the balloon is used to the expand the stent. The self-expanding stents may be made of shape memory materials such as Nitinol or constructed of other metals but of a design which exhibits self expansion characteristics.
In certain known stent delivery catheters, a stent and an optional balloon are positioned at the distal end of the catheter, around a core lumen. The stent and balloon are held down and covered by a sheath or sleeve. When the distal portion is in its desired location of the targeted vessel the sheath or sleeve is retracted to expose the stent. After the sheath is removed, the stent is free to self-expand or be expanded with a balloon.
A number of sheath designs are known in the art including those disclosed in U.S. Pat. No. 4,732,152 to Wallsten (""152), U.S. Pat. No. 4,848,343 to Wallsten (""343), U.S. Pat. No. 4,875,480 to Imbert, U.S. Pat. No. 5,662,703 to Yurek et al. (""703), U.S. Pat. No. 5,690,644 to Yurek (""644) and WO 94/15549, all of which are respectively incorporated herein in their entirety by reference, disclose using a sleeve formed of a doubled-over section of membrane to compress and contain the stent.
Wallsten ""152 and Wallsten ""343 disclose the use of lubricants on the interior walls of the membrane. Moreover, fluid may be introduced into the chamber that is formed, in part, by the walls of the doubled-over membrane.
The Imbert device contains small holes in the sleeve to allow for the expulsion of gas therefrom upon the introduction of a fluid into the region between the inner and outer walls. The holes are not sized to allow for fluid flow therethrough.
Yurek ""703 discloses a stent that is retained distal to the inner tube by a folded over sheath. The outer layer of the sheath, although not the inner layer, is disclosed as being porous. The Yurek ""644 patent and WO 94/15549 disclose a catheter in which a stent is mounted on an inner tube and retained by a double walled hose having micro pores in the outer wall of the hose. The micro pores allow for the flow of fluid therethrough. The Yurek catheter is of the rapid-exchange design.
U.S. Pat. No. 5,445,646 to Euteneuer et al., incorporated herein in its entirety by reference, discloses a stent delivery apparatus comprising a single layer sheath retaining sleeve means for retaining the stent in its delivery configuration attached to a slipping sleeve means for releasing the stent to self-expand. The slipping sleeves may be activated hydraulically by delivering a fluid to the area in between the inner and outer layers of the slipping sleeve.
While the use of rolling membranes is known, it is desirable to provide a medical device delivery system with a rolling retractable sheath in which the frictional interactions between the inner and outer walls of the sheath are reduced without requiring hydraulic activation. A rolling membrane eliminates the problem of sliding friction that is common with sliding sheaths as the rolling membrane, literally, rolls off of the stent. This, in turn, results in a lesser likelihood of the stent being damaged as the sheath is removed from over it. It is also desirable to provide a dual function stent delivery system wherein the sheath may function as an expansion balloon as well as a stent retaining sheath. It is also desirable to provide such a system with a partially sealed rolling retractable sheath to prevent any lubricants or inflation fluids interior to the sheath from interacting with any bodily fluids. It is also desirable to provide a system having a rolling retractable sheath whose inner and outer walls exhibits different physical properties such as hoop strength, expansion characteristics and creep resistance. The creep resistance of the outer wall is of particular value in preventing the stent from growing in profile and thereby deforming the catheter sheath.
The present invention addresses these needs in its various embodiments as described below.
The present invention provides a medical device delivery system which comprises an inner tube having a medical device mounting region at the distal region for concentrically mounting a medical device thereon and a rolling retractable sheath which may operate as a dilatation balloon and which retains a medical device on the inner tube and a retraction device.
The rolling retractable sheath, which includes a rolling double walled member, may be formed of a single member folded over on itself or of two different members joined together and folded over on itself. It is disposed concentrically about the inner tube. The inner wall of the double walled member is attached to the inner tube proximal to the medical device mounting region and the outer wall of the double walled member is attached to a retraction device. The inner wall preferably has a greater tendency to rollingly move upon the application of a rolling force than the outer wall.
An open ended chamber is formed by the inner and outer walls of the sheath. The open end of the chamber narrows at a point where it is in fluid communication with a proximally extending inflation lumen. The chamber may be filled with a fluid in order to cause at least the outer wall of the sheath to expand outward from the catheter. The various walls of the catheter may be constructed to allow the outer wall to have predetermined inflation properties which may differ from those of the inner wall.
The inner tube has a medical device mounting region at the distal region for concentrically mounting a medical device thereon. The sheath is retractable from a delivery position to a release position. In the delivery position, the sheath covers at least a portion of the medical device mounting region while in the release position, the sheath no longer covers the medical device mounting region.
The retraction device, which is operably connected to the rolling retractable sheath for retraction of the retractable sheath, moves the outer wall in a proximal direction relative to the inner wall so that the sheath no longer covers the medical device mounting region. When the sheath is used as dilatation balloon, during inflation of the sheath the retraction device may be used to position the sheath and to assist in preventing the sheath from moving off of the stent prior to delivery of the stent.
In another embodiment, the invention is directed to a medical device such as those described above in which the inner wall of the rolling retractable sheath is formed of at least a first material and the outer wall is formed of at least a second material different from the first material. The inner and outer walls may be adhesively bonded together, mechanically joined together or otherwise joined to each other.
In another embodiment, the inner and outer walls, respectively, may be constructed of a first material which rolls on retraction of the sheath and a second material which does not roll on retraction. In another embodiment the second material has a higher hoop strength than the first material. In yet another embodiment the outer wall material has a higher tensile strength than the inner wall material of the sheath. In yet another embodiment the outer wall exhibits a higher degree of longitudinal stiffness than the inner wall. In yet another embodiment the outer wall is more compliant than the inner wall. In yet another embodiment the outer wall exhibits a higher flexural modulus than the inner wall.
In the above embodiments where the inner and outer walls are made of different materials, the thickness of the inner and outer walls may also differ, further contributing to the desired properties of the walls.
In yet another embodiment of the invention, the inner and outer walls are made of the same material, the inner wall being thinner than the outer wall. The inner wall is thin enough to allow the inner wall to roll while the outer wall is sufficiently thick to resist rolling and prevent unwanted movement of the stent. Desirably, the thickness of the outer wall will be at least 1.5 times the thickness of the inner wall, more desirably, the outer wall will be at least 4 times the thickness of the inner wall.
In all of the above embodiments, a lubricant may, optionally, applied to at least a portion of the inner wall and/or outer wall.
Further, in all of the above embodiments, a pull-collar mounted at the distal end of the catheter in conjunction with a pull wire may be employed as part of the retraction device.
The invention is further directed to a stent delivery device comprising any of the above-described medical device delivery systems with a stent mounted on the medical device mounting region of the inner tube. Other device that may be delivered by the above described systems include grafts and vena cava filters.
The invention is also directed to a method of delivering a medical device to a desired bodily location. The method comprises the steps of providing medical device delivery system and a medical device, mounting the medical device on the medical device mounting region of one of the described medical device delivery systems, percutaneously inserting the medical device delivery system in a bodily lumen containing a bodily fluid, the bodily fluid optionally passing through the sheath so as to prime the medical device delivery system, traversing the bodily lumen until the desired bodily location is reached, optionally inflating the sheath to pre-dilate the body lumen, retracting the rolling retractable sheath proximally so as to expose the medical device and withdrawing the medical device delivery system from the bodily lumen. In a preferred embodiment, the medical device is a stent, optionally self-expanding, although other devices including grafts and vena cava filters may be similarly delivered.
Finally, the invention is directed to a medical device delivery system comprising an inner tube having a medical device mounting region at the distal region for concentrically mounting a medical device thereon, a rolling retractable sheath and a retraction device for retracting the rolling sheath. The rolling retractable sheath serves to retain a medical device around for about the inner tube. The rolling retractable sheath is formed of a double walled member forming an open chamber between the walls which is inflatable by being in fluid communication with a proximally extending inflation lumen. The sheath is disposed concentrically about the inner tube. At the proximal end, the rolling sheath is secured, directly or indirectly via a bumper or other securement device, to the inner tube proximal of the medical device mounting region. At the distal end, the rolling sheath is attached to a retraction device.
For the purposes of this disclosure, it should be noted that the term xe2x80x9cmedical device mounting regionxe2x80x9d is intended to apply to a region of an inner tube on which a medical device resides as well as a region of an inner tube over which a medical device resides. An example of the former is a region of an inner tube to which a stent is crimped. An example of the latter is a region over which a self expanding stent resides. Moreover, where reference is made to mounting a medical device on an inner tube, it is intended to include both mounting the device on and mounting the device over the inner tube.